Amplifier and two-phase motor control circuit



Sept. 10, 1963 J. o. VITALE 3,103,515

AMPLIFIER AND Two-PHASE MoToR CONTROL CIRCUIT Filed May 17, 1961 2 Sheets-Sheet 1 HTOR/VEY J. O. VITALE Sept. 1G, 1963 AMPLIFIER AND TWO-PHASE MOTOR CONTROL CIRCUIT Filed May 1'7, 1961 JNVENTOR. JOSEPH O. V/ 74LE BY United States Patent O Corporation,` Teterboro, NJ., a corporation 'of Delaware Fired May 17, 1961, ser. N0. 110,799 1s claims. (ci. 31e-2st) The present application is a continuation-in-part of US. application Serial No. 89,947, now abandoned, filed February 17, 1961, by Joseph O. Vitale and assigned to The Bendix Corporation.

Thel invention relates to an amplifier and two-phase motorcontrol circuit and more particularly to such a control cncuit in which there is provided in the amplifier an electronic iiow control means of a type such as an electronic valve having a plate, cathode and control grid or semiconductor device of a type such as a transistor havlng a collector, emitter and base and an output circuit to the control winding of the motor including a cathode or emitter follower circuit which in addition to transferring power from the amplifierto the motor control winding provides a Very high negative feedback which prevents oscillation in the output signal applied to the control winding so that the necessity of gain controls or a rate generatorfeedback in the control of the two-phase motor is effectively eliminated.

An object of the invention is to provide an ampiifier and two-phase motor control circuit having a high gain low power cathode or emitter follower circuit in the ampliiier output circuit to the control winding of they motor.

Another object of the invention is to provide an amplilier and two-phase servo motor control circuit in the low price range with good stability, high gain and good dependability.

Another objectof the invention is to provide an amplifier and two-phase servo motor control circuit in which the amplifier includes an electron fiow control device of a type having electrodes between which an electron flow may be effected and an electron flow control element, and in which there is provided a circuit for following a change in the electron. flow between said electrodes and serving as an output circuit from the amplifier to the control winding of the servo motor so as to eliminate the need for utilization of a conventional power transformer inl the output circuit as an impedance matching device, while in addition to providing forthe effective ltransfer of 'power from the amplifier tothe servo motor load the follower circuit further provides a very high negative feedback which serves to prevent oscillation in the control winding of the servo motor so as .to eliminate the need for utilization of the conventional gain controls or anti-hunting rate generator feedback circuits.

These and other objects and features of the invention are pointed out in the following description in terms of the embodiments thereof which are shown in the accompanying drawings. lt is to be understood, however, that the drawings are for the purpose of illustration only and are not a definition of the limits of the invention, reference being had to the appended claims for this purpose.

In the drawings:

FIGURE 1 is a schematic wiring diagram of an amplifier and two-phase motor controly circuit embodying the present invention.l

FGURE 2 is a schematic wiring diagram of a second form of the invention. v

' Referring to the drawing of FIGURE l, lines 1 and 3 lead from an A.C. control signal source indicated generally by the numeral 5 and of conventional type to the input of an amplifier 7. The'amplier 7 may be of a conventional two-stage type utilizing a pair of electronic "ice l valves `9 and 11 of the triode type in a conventional resistance-capacitance coupled circuit and having output lines 13 and 15 leading to the input of a power amplifier 16 utilizing an electronic valve 17 of the pentode type.

A source of electronic energy for operating the amplifiers 7 and 16 is indicated generally by the numeral 18 and may be of a conventional type. i

Output lines 19 and 21 lead from the power amplifier 16 to a control winding 23 of a two-phase servo motor 25 of conventional type having a fixed phase winding 27. There is further provided a phase shifting capacitor 29 in the line 19.

The power amplifier 16, as shown, may include the pentode type electronic valve 17 having a plate or anode elementV 31, a cathode or cathode element 33, a control grid or control electrode 35, ya screen grid 36, suppressor or cathode grid 37 and heater 38. The heater 38 is energized from outputconnections 39 from: the power source 1S while other output connections from the power source 13 including high voltage positive conductor 41 and i grounded conductor 43 are connected respectively to the plate 31 through-,a plate resistor 45 and to `the cathode 33 through the grounded connection 21 of the amplifier 116. A third conductor 47 from the powersource 18 is arranged so as to supply a potential to the screen grid 36 somewhat less positive tiran that supplied hy the conductor 41 to the resistor 45. The opposite end of the resistor 45 is connected to the plate 31 and through a conductor i3 tothe screen grid 35 and conductor 47.

Further connected in the circuit to the cathode 33 of the electronic valve 17 is a cathode follower circuit, including the cathode resistors and 52. The cathode resistor elements are connected across [the amplifier output lines 19 and 21.

Further included in the cathode follower circuit is a resistor element S4 having one end thereof connected to la point between the cathode resistoms 50 and 52 while the opposite end of the resistor Sli is connected to the control grid 35 of the electronic valve 17. Moreover through a coupling capacitor56, the control grid 35 and resistor 54 are coupled to the outputline 13 from the two-stage amplifier 7 The opposite output line 15 from the amplifier 7 is connected to the line 21 and through resistors 50 and 52 to the cathode 33 of the electronic valve 17. Further a capacitor 57 is shunted across the resistors 52 and vSti and `thereby across the inputto the control grid 35 and cathode 33 from the amplifier 7. The foregoing provides a cathode follower output through the lines 19 and 2110 the control winding 23 of the two-phase servo motor 25 which does not need to utilize the conventional inductionL type transformer for power 'transference to the control winding 23 of the two-phase servo motor 25.

Although the conventional transformer output is a good impedance matching device, it does not have the advantages which are present 4in the described cathode follower output in the transference of the controlling signal to the control winding 23 of the two-phase servo motor 2'5.

The cathode follower circuit provides a degenerative circuit in which an inverse feedback is obtained by way of the unbypassed cathode resistor elments Sil and 52 and across which the output -is taken through lines 19 and 21. This circuit also provides an impedance-matching or irnpedance-lowering device having less than unity voltage `gain but capable of producing power gain. lts high input impedance and very low output impedance render it particularly suitable for coupling between pulse-generating or pulse-transmitting stages of the amplifiers 7 and I16 and the output lines 19 and 21 leading to the circuit for the control winding 23 of the servo motor 25 and including the phase shifting capacitor 29.

of the transistor 157v while *the grounded input lead 131 is connected to one end off a resistor 161 connected at the opposite end by a .conductor 162 to the emitter of the transistor 157. The capacitor 153 efiects a further suitable shift in the phase of the A.C. signal applied therethrough to the hase of the transistor 157.

The lcollector of the transistor 157 is inv turn connected 'by a conductor 163 to the conductor 141 `leading to the negative terminal of the source of electrical energy 143. A resistor 165 isy connected between the conductor 163 yleading from the collector and lthe conductor 155 leading to the base of the transistor 157.

Output conductors 170 and -172` lead from opposite ends of the resistor 161 so as to provide `an emitter follower circuit coupled Iby a capacitor 175 to avariabl'e control Winding 176 of the two-phase servo motor 10T ,having a fixed phase winding 17 3 connected to the source of `alternating current. The capacitor 175 provides a D.C. )block to prevent the winding 176 from shunting the resistor 161. Further the capacitors 110, 125, 153 and 175 effect a total ninety (90) degree Ishift in the phase of the A.C. control signal applied therethrough to the winding 176 so as to cause the operation ofthe servo motor 107, as heretofore explained.

Further the emitter follower output applied through the lines 170 and 172 to the control wind-ing 176 of the ltwo-phase servo lmotor 107 ydoes not need to utilize the conventional induction type transformer for power transference to the control winding 176 of the two-phase servo motor 121. l

The emitter follower circuit provides la degenerative circuit in lwhich an inverse feedback is obtained by Way of the unbypassed emitter resistor 161 and across which the output is taken through'lines 170 and 172. This circuit also provides an impedance-matching or impedance-lowerin device having less than unity 4voltage Igain but capable of producing power gain. Its high input impedance and very llow output impedance render it particularly suitable for coupling between pulse-generating or pulse-transmitting stages tof the Iamplifiers 105 `and 106 xand the output linesv 170 and 172 leading to the circuit for the control winding 176 of the servo motor 107 and including the phase shifting capaci-tor 175.

In addition to the transfer of power from the amplifier 105 and 106 to the load of the controlled motor 107,

the emitter follower output to the lines 170l `and 172 follows the voltage of the input @control signal applied across the l-ine 131 and the line 155 to the base of the transistor 157 and hence is of the same polarity and provides good regulation because of -i-ts low impedance. The

` emitter follower circuit has Ia very high Vnegative feed-back `which prevents oscillation and eliminates the need for Vprovidinggain controls or a rate generator anti-hunting feedback signal.

Thus, if a .more positive signal is applied to the base of the transistor 157, a resulting decrease in the flow of the collector current through resistor 161 produces` a decrease in the `fall in potential across the resistor 161 making the conductor 162 more positive. Likewise a more negative signal applied to the base '.155 causes an l increase'in the fall in potential across the resistor 161 making the conductor 162 less positive. Thus the voltage across the emitter resistor I161 follows the signal voltage applied to the oase of the transistor 157 and in effect I tendsto reduce the voltage difference between the base and emitter of the transistor 157, as established by'ithe input signal, and in turn reduces the effectiveness `of the input signal so as to provide a retarding or negative feedback anti-hunting effect.

Further due to the selective arrangement of the amplifiers 105 and 106 in cooperative relation to the varistor circuit 104,. high gain amplification is provided for low range signals while high range signals areefiectively attenuated to prevent overdrive of the respective transistors 127 and 157 so as toathereby effect good sharp servo signals during both low and high range signals, while the emitter follower circuit including resistor 161 and output leads 170 land 172 in lfollowing the high gain low range signals, as the case may be, provides a very high negative feedback which prevents oscillation and eliminates the need for providing a rate generator antihunting feedback signal.

Although but two embodiments of the invention have been illustrated and described, various changes in the form and relative arrangements of the parts, which will now appear to those skilled in the art may be made without departing from the scope of the invention. Reference is, therefore, to be had to the appended claims yfor a definition of the limits ofthe invention.

What is claimed is:

l. In an amplifier and control circuit for a two-phase motor of a type including an electronic valve having an anode element, a cathode element and a control electrode, means for impressing a variable pulsating electrical input signal across said lcathode element and control electrode, and said two-phase motor having a fixed phase winding and a variable phase control windingincluding a phase shifting capacitor coupled with the control Winding; the improvement comprising a resistor serially connected in said control circuit with said cathode element and electrical conductors leading from opposite ends of said resistor for directly transferring a controlling pulsating output signal across said control winding and phase shifting capacitor coupled thereto.

2. In an amplifier and control circuit for a twophase motor of a typ-e including an electronic valve having an anode element, a cathode element and a control electrode, means for impressing a variable pulsating electrical input signal across saidcathode element and control electrode, and said two-phase motor having a fixed phase winding and a variable phase control winding including a phase shifting capacitor coupled with the control winding; the improvement comprising a first resistor serially connected in said control circuit with said cathode element, electrical conductors leading yfrom opposite ends of said first resistor for directly transferring a controlling pulsatingoutput signal across said control winding and phase shifting capacitor coupled thereto, and a second resistor connected at one end to said first resistor and through at least a part of said first resistor to said cathode element and at an opposite end to said control electrode to provide a high negative feedback through said second resistor to the control electrode to prevent oscillation of the controlling pulsating output signal.

3. In an amplifier and control circuit for a two-phase motor of a type including an electronic valve having an anode element, a cathode element and a control electrode, means for impressing a variable pulsating electrical input signal across said cathode element and control electrode, and said two-phase motor 4having a fixed phase Winding and a Vvariable phase control winding including ling pulsating output signal across said control lwinding and phase shifting capacitor coupled thereto, a second resistor connected at one end to said first resistor and through at least a part of said first resistor to said cathode element and at an opposite end to said control electrode to provide a high negative feedback through said second resistor to the control electrode to prevent oscillation of vthe controlling pulsating output signal, and a capacitor coupled between said control electrode and said interconnected first and second resistors'to stabilize the input signal impressed across said cathode element and control electrode by smoothing out transient iiuctuations therein,

4. ln `an amplifier and control circuit for a twophase motor of a type including an electronic valve having an anode elemente cathode elementand` a control electrode, means for limpressing a variable pulsating electrical input signal across said cathode element and control electrode, and said two-phase motor Yhaving a fixed phase Winding and Va variable phase control Winding including a phaseV shifting capacitor coupled with the control winding; the improvement comprising a iirst resistor and `a second resistor seriallyconnectedin said control circuit with said cathode element, Yelectrical conductors leading from opposite ends of therserially connected iirst. and Y .second'resistors and directly'transferring.acontrolling pulsating output signal across said control winding and phase shifting capacitor coupled thereto, Ya third resistor connected yat one end to said'control electrode and at an opposite endgto said- 1Vtirst and secondY resistors 1 aefa point.

between said serially connected resistors-and lthrough said rst resistor to said cathode element so as to permit operationof the electronic valve over a Wide range of VinputV signals impressed across said cathode element andV Y control Yelectrode while providing a high negative` feedback'throughsaid third resistor to the control electrode to prevent oscillation of the controlling pulsatingoutput signal.

5. In an amplifier and control circuit for a two-phase motor of a type including an electronic valve having an Y anode element, a cathode element and a control electrode, means [for impressing a variable pulsating electricalV input signal across said cathode element and con-Y trol electrod-e, and said two-phase motor having-a fixedy phase Winding and .a variable phase control winding in-v j cluding a phase shifting capacitor coupled with the Ycontrol winding; the improvement comprising a first resistor Y and a second resistor serially connectedin said control circuit with said cathode element, electrical conductors leading frornopposite ends of the seriallyconnected irst and Vsecond resistors and directly transferring a controlling pulsating output signal across said-control winding and serially connected phase shift-ing capacitorV coupled thereto, ra third resistor connected at one end to said controlelectrode and at an opposite end to said tirst and second resistors at a point between said serially connected resistors and through said iirst resistor to said cathode element so as to permit operation ofthe electronic valve` overa 'wide range `of 4input signals impressed across'said cathode element and control electrodel while providing a i high negative feedback through said third resistor to the control electrodeto prevent oscillation of the controlling pulsating youtputsignal, and a capacitor electrically connected to'said control electrodeyand across said second and third resistors to stabilize the input signal impressed Y acrosssaid cathode element and control electrode from Y.transient `fluctuations therein.

6.1The combination comprising yan electronicl valve having :an anode element, a cathode elementwand a control eleetrode, means for impressing a variable pulsating electrical input signal on said control electrode,V a two- Y phase control Winding, a'resistor serially connected in circuit with saidl cathode element, said resistor connected across a pair of electrical output conductors, one of said output conductors effecting an electrical connection to one end of lthe control Winding of said two-phase motor,

conductors to another end of said control Winding so as to apply a controlling pulsating electrical output signal across said control winding.

Y "phase motor havinga fixed phase winding :and a variable and Ya capacitor for coupling the other of said output V7. ,The combination comprising a two-phase motor` having a ixedrphase winding and a-fvariable phase control winding, an electronic kvalve having an anode ele` ment, a cathode element, :and a control electrode, a `resistor connected at 'one end to said cathode element,

means for impressing a variable pulsating electrical input n y signalV to said control Velectrodeandv other end of saidre- 7 sistor and through said resistor to said cathodefelement, said resistor ,Connected across a pair of electrical output conductors, one'of said output conductors `effectir'lg an electrical connection to one `end of the control winding of said two-phase motor, a capacitor for coupling the other of said output conductors to another end of said control Winding so as 'to apply a controlling pulsating electrical Aoutput signal across said control winding, and

anotherV capacitor connected between said `control electrode and said other end of said resistor so as'to stabilize `the impressed input signal.. Y s Y 8. The `combination comprising a two-phase motor having :a fixed phase A,winding Yand a'variable phase .control winding, an electronic valve: having an anode ele-,f

ment, a cathode element, and a control electrode, a re'- sistor connected at one end to said cathode element,

means forlimpressing -a variable pulsating electrical input f signal 4to said control electrode and other end Vof saidY resistor and through said resistor to said cathodeelement, said resistor connected across a pair of electrical output conductors, one Yof said-outputrconductors effecting an electrical connection to onecnd of 'the control winding .ofy said two-phase motor, a capacitor for cou- Y plingy the other of said output conductors to another endV of said control winding so as to apply acontrolling pulsating electrical `outputV signal across said Vcontrol wind- Ving, andV another resistor connected between Vysaid control electrode and the first-mentioned resistor and through Yat least a portion of said inst-mentioned resistor toV said` cathode elementso as to provide ahigh negative feedback through said other resistor to the control electrodeV Vsaid ristor connected across a pair of electrical output conductors, one of said output conductors electing an electrical connection to one end Vof the control Winding of said two-phase motor', a capacitorwfor coupling the other ot saidroutput conductors Vto another endof said control winding so as Vto apply a ,controlling pulsating electrical output signal across ysaid control winding,r another resistor connected between said control-electrode,r :andthe first-intentionsdfresistorand through atleast ay portion of said lirst-mentioned resistor to said cathode element sov as to providey 4a high negative feedback through f said other resistor to the control-electrode to prevent oscillation vof thecontrolling pulsating output signal, and

another capacitorconnected between said" control elec-VV trode and said other end of said Erst-mentioned resistor so as to stabilize lthe impressed input signal.

10. @Invert amplifier .andcontrolcircuit for a two-phase,V

motor of a type including an electron flow control device having electrodes betweeny which an electron flow may be Y effected and an electron ilow controlelcment, means `for impressing a variableV pulsating electricalinput signal to said electron flow control element, and said two-phase motor having a lixed phase winding land a variable phase control Winding including a phase `shifting capacitor coupled lwith the control Winding; the improvement comprising a resistor serially connected in said control circuit with said electrodes, [and electrical conductors leadingfrom |opposite ends of said resistor for directly transferring a controlling pulsating `output signal across said control winding Yland phase shifting capacitor coupled thereto.Y

1l. The combination comprising an electncn ow cOnv trol device having electrodes between which an electron ilow maybe effected and an elcctron'low control element,VY f Y means jfor impressnga'variable pulsating electricalffinputf Y f signal on said control element, a two-phase motor having la fixed phase Winding and a variable phase control winding, a resistor serially connected in circuit with said electrodes, said resistor connected across a pair of electrical output conductors, one of said output conductors eiecting an electrical connection to one end of the control Winding tot said two-phase motor, and a capacitor for coupling the other of said output conductors to another end ou? said :control Winding so as to apply a controlling pulsating electrical output signal across said control Winding.

12. In an amplifier and control circuit for a two-phase motor of a type including a transistor having a collector element, yan emitter element and a base element, means for impressing a variable pulsating electrical input signal across said base and emitter elements, Iand said two-phase motor having a fixed phase Winding and a variable phase control Winding including a phase shifting capacit-or coupled With the control winding; the improvement comprising a resistor serially connected in said control circuit with said emitter element, and electrical conductors leading from yopposite ends of said resistor for directly transferring la controlling pulsating ioumut signal across said control Winding and phase shifting capacitor coupled thereto.

13. The combination comprising a transistor having a collector, an emitter and a base, means for impressing variable pulsating electrical input signals .on `said base, a two-phase motor having a fixed phase windinglan'd a variable phase control Winding, .a resistor serially connected in circuit with said emitter, -a pair or electrical output conductors leading from opposite ends of said resistor, fone of said output conductors ellecting an electrical connection to one end of the control Winding of said twoaphase motor, and a capacitor for coupling the other lor said output conductors to another end of said control Winding so Ithat said output conductors :apply :controlling pulsating electrical output signals across said control winding due to a fall in potential across said resistor, and lsaid fall in potential causing a retarding signal to be applied to said emitter which follows a clran-ge in the controlling electrical input signal impressed on said base to prevent oscillation .in the controlling voutput signals applied across the control Winding of said motor.

14. The combination comprising a transistor having a collector, an emitter `and la base, control means for supplying Variable pulsating electrical control signals, a varistor circuit means to attenuate saidcon'trol `signals of an arnplitude in excess of a predetermined Valve and substantially uneifect other of said control signals of an yamplitude less than said predetermined value so as to provide resulant control signals of an amplitude less than a predetermined maximum Value, means for amplifying said resultant signals so that there may tbe effected a high gain in the amplitude off said other control sign-als and said attenuated control signals within a predetermined loper- Vating range of values, a tvwoaphase motor shaving a fixed phase Winding and a variable pli-ase control Winding, a resistor serially connected in circuit with said emitter and collector, means for impressing the resultant amplied signals on said base rand through said resistor on said emitter, a pair of electrical output conductors leading lfrom opposite ends lor said resistor, one of said output conductors effecting an electrical connection to one end of the control winding of said two-phase motor, and a capacitor for coupling the other of said output conductors to another end of said control winding so lthat said output conductors apply controlling pulsating electrical output signals across said control Winding due to a fall in potential across said resistor, and said fall in potential causing a retarding sign-al to be applied to said emitter which follows a change in the controlling electrical input signal impressed on said base to prevent oscillation in the controlling output signals applied across the control Winding of said motor.

15. The combination comprising a transistor having a collector, an emitter and a base, control means for supplying variable pulsating electrical control signals, varistor circuit means including a pair of oppositely pioled `silicon carbide diodes for attenuating said control signals having an amplitude in excess oct a predetermined value and substantially uneiect other of said control signals of an amplitude less than said predetermined value so as to provide resultant control signals of -an amplitude less than a predetermined maximum value, means for amplifying said resultant `signals so that there may be effected a high gain in the amplitude of said other control signals fand said attenuated control signals Within a predetermined operating range of values, a twoephase motor having a xed phase winding anda variable phase control Winding, la resistor serially connected in circuit with lsaid emitter and collector, means `for impressing the resultant amplified 'signals Ion said base and through said resistor on said emitter, a pair of electrical output conductors leading from opposite ends of said resistor, one of said output conductors effecting an electrical connection to one end of the control winding of said two-phase motor, and a capacitor `for coupling the other of said output conductors to another end of said control winding so that said output conductors apply controlling pulsating electrical output signals across said control winding due to a fall in potential `across said resistor, land said fall in potential causing a retarding signal to be applied .fto said emitter which follows a change in the controlling electrical input signal impressed on said base to prevent oscillation in the controlling output signals applied across the control Winding of said motor.

References Cited in the le of this patent UNlTED STATES PATENTS 

1. IN AN AMPLIFIER AND CONTROL CIRCUIT FOR A TWO-PHASE MOTOR OF A TYPE INCLUDING AN ELECTRONIC VALVE HAVING AN ANODE ELEMENT, A CATHODE ELEMENT AND A CONTROL ELECTRODE, MEANS FOR IMPRESSING A VARIABLE PULSATING ELECTRICAL INPUT SIGNAL ACROSS SAID CATHODE ELEMENT AND CONTROL ELECTRODE, AND SAID TWO-PHASE MOTOR HAVING A FIXED PHASE WINDING AND A VARIABLE PHASE CONTROL WINDING INCLUDING A PHASE SHIFTING CAPACITOR COUPLED WITH THE CONTROL WINDING; THE IMPROVEMENT COMPRISING A RESISTOR SERIALLY CONNECTED IN SAID CONTROL CIRCUIT WITH SAID CATHODE ELEMENT AND ELECTRICAL CONDUCTORS LEADING FROM OPPOSITE ENDS OF SAID RESISTOR FOR DIRECTLY TRANSFERRING A CONTROLLING PULSAT- 